Is he talking about NAT'ing at layer 3? From what I understand, he wants to forward anything from his (probably single) external IP to multiple internal IPs. Like you said, that doesn't work. The closest thing I can think of is a Loadbalancer, but one that works at layer 3? Probably not. CARP could do, but you need a dedicated external IP and a shared one between all CARP members, as far as I know.

How is this person in charge of designing the system without any freaking clue about where the hypervisor is installed too, what the array configuration should look like and lastly what and why an OBR is better than splitting arrays!